The present invention relates to photographic apparatus in general, especially to continuous microfilming cameras, and more particularly to improvements in cameras of the type wherein minute stray movements of photographic film relative to the lens or vice versa can greatly affect the quality of exposures.
It is known to maintain the lens of a microfilming camera at a substantially constant distance from the emulsion-coated side of the film by providing the support for the lens with several positioning rolls which contact the emulsion-coated side and by urging a spring-biased pressure plate against the uncoated side of the film opposite the positioning rolls. The film is moved lengthwise by several driven rollers which are remote from the positioning rolls. Reference may be had to the commonly owned German Utility Model No. 6,946,380. Such transport of film between the positioning rolls and the pressure plate insures that the distance between the lens and the emulsion-coated side does not vary in response to fluctuations in the thickness of the film. However, the transporting rollers cannot insure that the speed of the film remains constant or that such speed fluctuates within a sufficiently narrow range. For example, uneven transport of film may be due to lack of synchronization between the drive means for the transporting rollers. Fluctuations in the speed of lengthwise movement of film are particularly undersirable in continuous microfilming cameras.